Transformation Properties Research Articles

Tailoring the microstructure and mechanical properties of H13 steel by controlling the pre-precipitation of VC carbides from austenite

Carbides play an important role in influencing the phase transformation and mechanical properties of steels. In this work, the microstructure of H13 steel is tailored by controlling the pre-precipitation of VC carbides at 950 °C to obtain excellent mechanical properties. It is revealed that the pre-precipitation of VC carbides decreases the carbon content of austenite, thus resulting in a high temperature of Ms. With the increasing amount of pre-precipitated VC carbide, martensite transformation is firstly accelerated by the enhanced transformation driving force, and then decelerated due to the hindering effect of VC particles on the growth of martensite laths. The improvement in strength, ductility and toughness of quenched H13 steel can be attributed to the pre-precipitated VC carbides and the refined martensite blocks. The tempered H13 steel with pre-precipitated VC carbides also exhibits excellent ductility and toughness. It can be concluded that controlling the pre-precipitation of VC carbides from austenite is an effective method to tailor the mechanical properties of H13 steel.

The Significance of Limitations and Properties of Lorentz Transformation in Teaching

Widely misused calculator is a Lorentz transformation. It is a calculator that calculates or transforms co-ordinates of the point between two relatively moving inertial reference frames with uniform rectilinear velocity in relation to each other. This calculator shows its works at the end of the event. Means when light reach from event point to the origin of the each moving reference frame. So, in a time t, when light from the event point reach to the origin of each reference frame, a moving reference frame moves a distance vt during that same interval which is shown as "t" in "vt". This is the basic understanding of the situation used in the Lorentz transformation. This confirms the restrictions shown in the article. The Lorentz transformation is applicable only with these restrictions.

Polyoxotungstate Featuring Zinc-Ion-Triggered Structural Transformation as An Efficient Electrolyte Additive for Aqueous Zinc-Ion Batteries.

It is promising but still challenging for the widespread application of aqueous zinc batteries due to the poor reversibility of the Zn anode caused by prevalent dendrite growth and pronounced interfacial s ide reactions. Herein, we report a rare soluble and water-stable high-nuclearity {Nd9Si4W39} polyoxotungstate. Interestingly, upon encountering Zn2+ ions, the discrete {Nd9Si4W39} nanocluster undergoes a structural transformation to form an infinitely extended cluster-based {[Zn(H2O)4]3[Nd9Si4W39]2} two-dimensional honeycomb layer, with which atomic-level Zn2+ ion effects in reconstructing the layer are determined. More interestingly, we demonstrate that the structural transformation property renders the {Nd9Si4W39} cluster an efficient electrolyte additive for aqueous zinc batteries, enabling the formation of the 2D layer as a protective layer on the zinc anode, significantly enhancing the reversibility of the zinc anode. Compared to the pristine Zn//Zn symmetric battery, the Zn//Zn symmetric battery with the {Nd9Si4W39} additive exhibits an extended lifespan of over 2000 hours at a current density of 1 mA cm-2. In-situ optical microscopy, Raman spectroscopy, and molecular dynamics simulations reveal that the formation of the protective layer effectively promotes uniform zinc deposition, and inhibits zinc agglomeration, dendrite growth, and side reactions, thereby enabling the zinc anode to exhibit high reversibility and long-term service life.

Ni transformation and hydrochar properties during hydrothermal carbonization of cellulose

The harm of heavy metals to the environment and human health has become a major concern due to their high toxicity, ease of accumulation in the human body, and resistance to degradation. In particular, Ni is widely used in various industrial and consumer products, which is a toxic pollutant posing great harm to humanity and the environment. Hydrothermal carbonization has broad prospects for reducing the ecological toxicity of heavy metals. However, the effects and mechanisms of hydrothermal carbonization conditions on the stabilization of heavy metals still need to be further explored. This research aimed to explore Ni migration and transformation within cellulose throughout the hydrothermal carbonization process. The results indicated that hydrothermal carbonization facilitated the immobilization of heavy metals due to the generation of hydrochars with complex surface structures. In addition, the hydrothermal carbonization process significantly decreased the weakly bound parts of Ni, thereby reducing the environmental risk of Ni. The optimal conditions for the hydrothermal carbonization process of cellulose added with Ni were 250 ℃ and 90 min. However, further increasing the reaction temperature or retention time resulted in negligible or even negative effects on Ni immobilization. In general, this study proposed possible mechanisms for the effects of hydrothermal carbonization on the migration and immobilization of heavy metals, which may provide insights into handling heavy metals in biomass.

Microstructure transformation and mechanical properties of Co68AlxFe24.7-xV4.8Cr2.5 high-entropy alloys with dual-phase structures

Here, we designed Co68AlxFe24.7-xV4.8Cr2.5 (x = 16.5,17 and 18 at.%) high-entropy alloys (HEAs) by adjusting the atomic ratio of Fe and Al elements and successfully prepared a series of eutectic or near-eutectic HEAs by direct casting method. All designed HEAs exhibit a dual-phase eutectic or near-eutectic structure containing FCC and B2 phases. As the Al content increases from 16.5 to 18 at.%, the microstructure of the designed HEAs evolves from eutectic structure to hypereutectic structure. Among the studied HEAs, Co68Al16.5Fe8.2V4.8Cr2.5 HEA with eutectic structure exhibits an excellent strength-plastic combination, i.e., the yield strength of 761 MPa, the ultimate compressive strength of 2178 MPa and the fracture strain of 21.9 %, respectively. Such an excellent mechanical performance is mainly attributed to dislocation strengthening and interface strengthening. Furthermore, the stable K-S orientation relationship between FCC and B2 phases endows this HEA with remarkable strength-ductility combination. The design strategy in this work can provide new ideas for the development of high-performance dual-phase HEAs.

Influence of Cold Drawing on Phase Transformation and Tensile Properties of FeCrMn Austenitic Stainless Steel 201

Manganese stabilizes the austenite and reduces the stacking fault energy in face‐centered cubic (FCC) structures, promoting the formation of hexagonal and cubic structures. This study investigates the phase transformation and mechanical behavior of extremely low‐carbon FeCrMn austenitic stainless AISI 201 steel subjected to cold drawing in three stages, ultimately reaching a true strain of 0.93. The objective is to examine the transformation from the parent FCC structure to hexagonal close‐packed and body‐centered cubic structures as a combination of transformation‐induced plasticity and twinning‐induced plasticity phenomena. X‐ray diffraction and electron backscatter diffraction analyses are utilized to investigate phase transformations under significant plastic deformation and the crystallographic orientation relationships between phases. Additionally, tensile and hardness tests are performed to assess the impact of plastic deformation on mechanical properties. Results indicate that a true strain of 50% is optimal for balancing strength and ductility in CrMnFe austenitic stainless steel. After applying a true strain of ε1 = 26.7%, yield strength (YS) increases by 192% and ultimate tensile strength (UTS) by 35%, while elongation reduces by 41%. With a further strain of ε2 = 57.5%, YS increases by 71% and UTS by 44%, but elongation drastically decreases by 94%. Applying the final strain of ε3 = 94.0%, YS and UTS only increase by 3% and 2%, respectively, while elongation further reduced by 40%. These findings suggest that a true strain of 50% shall be considered the maximum reduction for maintaining a balance between strength and ductility in CrMnFe austenitic stainless steel.

Repetitive corrugation and straightening (RCS) of NiTi shape memory alloy strip product

ABSTRACT Repetitive corrugation and straightening (RCS) is a novel method of severe plastic deformation in bulk metallic materials. In this study, the effect of RCS on the properties of NiTi shape memory alloy (SMA) is investigated. Cold-rolled (CR) Ni49.8–Ti50.2 (at. %) strips with varying degrees of cold-work were subjected to RCS and evaluated for transformation, mechanical and functional properties. The study demonstrated that RCS can be used effectively to improve the strength and ductility of the CR SMA strips, while its transformation and functional properties are largely preserved. The ultimate tensile strength (UTS) and elongation to failure of the 30% CR strip post RCS increased from 950 MPa to 1130 MPa and ~19% to ~26%, respectively. The microstructural evaluation confirmed that RCS resulted in notable grain refinement and re-distribution of Ti2Ni second phase in the matrix. Consequent to its high strength, the cyclic response of the RCS strip on stress-free thermal cycling was found to be better than the CR strip.

Comparison study on the effect of oxygen, nitrogen and hydrogen absorption on phase transformation and mechanical properties of quenched CP Ti and Ti6Al4V alloy

Microstructures and mechanical properties of commercial pure Ti and Ti6Al4V metal were studied after water quenching. The nitrogen (N), oxygen (O) and hydrogen (H) analysis was conducted on the quenched samples to establish the effect of impurities on phase transformation and mechanical properties. It was found that despite some negligible increment on the impurities, they could not be attributed to structural change but rather stabilization of the metastable FCC induced by rapid cooling. The formation of the metastable FCC phases was attributed to stresses induced by high cooling rates upon water quenching. Quenching from high temperatures has a significant effect on the crystal structure, microstructure and mechanical properties.

High-Precision Measurement Method for Small Angles Based on the Defect Spot Mode of the Position-Sensitive Detector.

The paper proposes and verifies a small-angle measurement method based on the defect spot mode of the position-sensitive detector (PSD). With the output characteristics of the PSD in the defect spot mode and the size transformation properties of a focused beam, the measurement sensitivity can be significantly improved. Calibration experiments with the piezoelectric transducer (PZT) indicate that compared with the current PSD-based autocollimation method, the proposed method can improve the sensitivity of small-angle measurement by 57 times, and the measurement sensitivity of the proposed method can be further improved by optimizing the system parameters, while the proposed method has the advantages of a simple system and high real-time performance. Therefore, the proposed method is expected to be used in high-precision motion error detection, as well as in shape and position measurement.

Microstructural evolution, phase transformation, and mechanical properties of Corrax-Ta40Nb60C-VC composite using vacuum sintering, solid-solution, sub-zero, and aging treatments

This study examined the effects of adding varying ratios of Ta40Nb60C and VC powders to Corrax maraging stainless steel powders, followed by vacuum sintering at temperatures ranging from 1385°C to 1430°C for one hour. The optimal sintering conditions were identified as 1415°C with 0.1 mass% Ta40Nb60C and 0.4 mass% VC additives. Under these conditions, the Corrax composite exhibited an apparent porosity of 0.16±0.07 %, a transverse rupture strength (TRS) of 2275.6±32.5 MPa, and a hardness of 67.2±0.6 HRA. After undergoing solid-solution, sub-zero, and aging treatments, the mechanical properties significantly improved, with TRS increasing to 2683.3±100.1 MPa and hardness to 76.3±0.5 HRA. The TEM and EBSD analyses indicate the presence of lath-shaped martensite, MC-type carbides, and M23C6-type carbides, contributing to enhanced mechanical strength. These findings suggest that adding Ta40Nb60C and VC powders and specific heat treatments significantly improves the mechanical properties of Corrax composites.

Investigation of phase transformation and mechanical properties of silicon addition on AlCrFeMnNi high entropy alloys

Abstract This paper examines the impact of silicon in the AlCrFeMnNi high-entropy alloy system, focusing on both its microstructural and mechanical properties. Alloys with varying silicon content (x = 0, 0.3, 0.6, 0.9 atomic ratio) were synthesized using vacuum arc melting. The phase formation of these high-entropy alloys was analyzed using X-ray diffraction to comprehend the alloying process behaviour. The findings revealed that the solidification of the AlCrFeMnNi alloy occurred in dendritically, with dendrite cores containing Cr, Fe, and Ni, while interdendritic regions were enriched in Al and Ni after adding Silicon. Increasing the silicon content from 0 to 0.9 led to significant improvements in microhardness and wear resistance. This improvement is attributed to the reinforcement of grain boundaries provided by silicon. The formation of an Al and Ni rich B2 phase is crucial in resisting dislocation motion and preventing further deformation. Additionally, the addition of silicon led to improved corrosion resistance, as demonstrated by potentiodynamic polarization measurements. However, a trade-off was observed between compressive strength and ductility: compressive strength increased with higher silicon concentrations, but at the expense of ductility.

Policy Iteration-Based Learning Design for Linear Continuous-Time Systems Under Initial Stabilizing OPFB Policy.

Policy iteration (PI), an iterative method in reinforcement learning, has the merit of interactions with a little-known environment to learn a decision law through policy evaluation and improvement. However, the existing PI-based results for output-feedback (OPFB) continuous-time systems relied heavily on an initial stabilizing full state-feedback (FSFB) policy. It thus raises the question of violating the OPFB principle. This article addresses such a question and establishes the PI under an initial stabilizing OPFB policy. We prove that an off-policy Bellman equation can transform any OPFB policy into an FSFB policy. Based on this transformation property, we revise the traditional PI by appending an additional iteration, which turns out to be efficient in approximating the optimal control under the initial OPFB policy. We show the effectiveness of the proposed learning methods through theoretical analysis and a case study.

Comprehensive Insight into Regular Damped Oscillatory Structures from Effective Electromagnetic Form Factor Data of Some Mesons and Nucleons

Regular damped oscillatory structures from the “effective” electromagnetic form factors of the hadrons h=π±,K±,K0,p,n were investigated. The “effective” electromagnetic form factor behaviors were calculated from the experimental data on the total cross-sections σtot(e+e−→hh¯) with errors. The apparent oscillations were observed for the first time for the proton, and we show, also taking other hadrons into consideration, that they are an arbitrary artifact resulting from a very simplistic theoretical description based on an elementary three-parameter model. If the data are described by a more appropriate and physically well-founded Unitary and Analytic model, then the oscillations disappear. In spite of this, if the three-parameter model is used to describe the “effective” electromagnetic form factor data, an interesting phenomenon is observed. The oscillations are opposite for particles which form an isospin doublet. By using the physically well-founded Unitary and Analytic model, it is demonstrated that this feature originates from the special transformation properties of the electromagnetic current of the corresponding particles in the isotopic space.

Rac1 GTPase Regulates the βTrCP-Mediated Proteolysis of YAP Independently of the LATS1/2 Kinases.

Background: Oncogenic mutations in the KRAS gene are detected in >90% of pancreatic cancers (PC). In genetically engineered mouse models of PC, oncogenic KRAS drives the formation of precursor lesions and their progression to invasive PC. The Yes-associated Protein (YAP) is a transcriptional coactivator required for transformation by the RAS oncogenes and the development of PC. In Ras-driven tumors, YAP can also substitute for oncogenic KRAS to drive tumor survival after the repression of the oncogene. Ras oncoproteins exert their transforming properties through their downstream effectors, including the PI3K kinase, Rac1 GTPase, and MAPK pathways. Methods: To identify Ras effectors that regulate YAP, YAP levels were measured in PC cells exposed to inhibitors of oncogenic K-Ras and its effectors. Results: In PC cells, the inhibition of Rac1 leads to a time-dependent decline in YAP protein, which could be blocked by proteosome inhibitor MG132. This YAP degradation after Rac1 inhibition was observed in a range of cell lines using different Rac1 inhibitors, Rac1 siRNA, or expression of dominant negative Rac1T17N mutant. Several E3 ubiquitin ligases, including SCFβTrCP, regulate YAP protein stability. To be recognized by this ligase, the βTrCP degron of YAP (amino acid 383-388) requires its phosphorylation by casein kinase 1 at Ser384 and Ser387, but these events must first be primed by the phosphorylation of Ser381 by LATS1/2. Using Flag-tagged mutants of YAP, we show that YAP degradation after Rac1 inhibition requires the integrity of this degron and is blocked by the silencing of βTrCP1/2 and by the inhibition of casein kinase 1. Unexpectedly, YAP degradation after Rac1 inhibition was still observed after the silencing of LATS1/2 or in cells carrying a LATS1/2 double knockout. Conclusions: These results reveal Rac1 as an oncogenic KRAS effector that contributes to YAP stabilization in PC cells. They also show that this regulation of YAP by Rac1 requires the SCFβTrCP ligase but occurs independently of the LATS1/2 kinases.

Stress-induced martensite transformation and mechanical properties of fine-grained Ti-10V-2Fe-3Al alloy fabricated by friction stir processing

Ti-10 V-2Fe-3Al, as the metastable β-type titanium alloy, has several applications in the aerospace industry due to its good mechanical properties. However, the study of stress-induced martensitic transformation behavior and corresponding mechanical properties in its small-sized grains (<20 μm) needs to be further clarified. This study investigates the relationship between grain size, stress-induced martensitic transformation, and mechanical properties of Ti-10 V-2Fe-3Al after friction stir processing. When the spindle speed increased from 200 rpm-100 mm/min to 350 rpm-100 mm/min, the grain size grew from 7.53 μm to 13.06 μm, and the martensite triggering stress decreased from 287 MPa to 111 MPa. The phase boundaries formed by α" and β, as well as the grain boundaries formed by α" and α", enhanced the plasticity of Ti-10 V-2Fe-3Al. The Crussard-Jaoul analysis method was used to investigate the effect of stress-induced martensitic transformation on Ti-10 V-2Fe-3Al, it was found that the martensitic transformation leads to dynamic softening. The formation of α" martensite results in an increased work hardening rate.

Three-point functions of higher-spin supercurrents in 4D N=1 SCFT: General formalism for arbitrary superspins

We analyze the general structure of the three-point functions involving conserved higher-spin “vectorlike” supercurrents Js(z)≔Jα(s)α˙(s)(z) in four-dimensional N=1 superconformal field theory. Using the constraints of superconformal symmetry and superfield conservation equations, we utilize a computational approach to analyze the general structure of the three-point function ⟨Js1(z1)Js2′(z2)Js3′′(z3)⟩ and provide a general classification of the results. We demonstrate that the three-point function is fixed up to 2 min(si)+2 independent conserved structures, which we propose to hold for arbitrary superspins. In addition, we show that the conserved structures can be classified as parity-even or parity-odd in superspace based on their transformation properties under superinversion. Published by the American Physical Society 2024

Bimodal grain structure, phase transformation, and mechanical properties of a Mg-Gd-Y-Zn-Zr alloy during hot extrusion

In this study, we investigated the evolution of grain structures and second phases of a Mg-9.5Gd-4Y–2Zn-0.3Zr alloy during two-stage deformation that took place in the metal during hot extrusion, as well as their effects on its mechanical properties. We found that the alloy exhibited a bimodal grain structure consisting of equiaxed dynamic recrystallized (DRXed) grains and elongated unDRXed grains. As the extrusion process progressed, DRX occurred on a large scale, resulting in an increase in the proportion of DRXed grains from 17.8% to 93.2%, and a reduction in average grain size from 80.3 μm to 9.41 μm. The grain orientation also underwent a transition from a single orientation of an extrusion direction (ED) parallel to <0001> (i.e. ED//<0001>) to mixed orientations of ED//<01–10> and ED//<0001>. The primary mechanism of dynamic recrystallization (DRX) during extrusion involved particle-stimulated nucleation (PSN) accompanied by both continuous and discontinuous DRX. The Mg-9.5Gd-4Y–2Zn-0.3Zr alloy mainly contained intergranular 18R-long period stacking order (LPSO) phases and intragranular 14H-LPSO. As the extrusion process progressed, 18R-LPSO changed from blocky to lamellar to accommodate deformation, and β-Mg5(Gd,Y) phase particles dynamically precipitated along DRXed grain boundaries. The 14H-LPSO phase was found to be primarily distributed within coarse unDRXed grains. As deformation via extrusion progressed, the quantity of 14H-LPSO gradually decreased. Ultimately, with the gradual dissolution of Mg5(Gd,Y), 14H-LPSO reprecipitated within the recrystallized grain boundaries. As the extrusion process progressed, both the yield strength (YS) and elongation (EL) increased from 132.6 MPa to 287.6 MPa and from 10.8% to 15.5%, respectively. This was mainly attributed to the significant reduction in grain size and second phase size.

Effect of cast part size on the microstructure and mechanical properties of a bainitic High-Carbon and High-Silicon Cast Steel

This study aims at assessing the impact of casting size on the bainitic transformation, resulting microstructures, and tensile properties of a high-carbon, high-silicon steel austempered at different temperatures. The casting size was analyzed by using Y blocks of two different thicknesses. The microsegregation, a common occurrence in cast parts, leads to different bainitic transformation rates at the microscopic scale. Specifically, interdendritic areas with higher alloying contents exhibit a slower transformation, resulting in a lower degree of transformation and a higher amount of blocky austenite. Despite differences in solidification structure and distribution of alloying elements, samples obtained from the thinner and thicker Y blocks yield comparable transformation times and mechanical properties, leading to enhanced uniformity in the mechanical behavior of the entire component. However, it is essential to ensure that the bainitic transformation is completed to minimize the detrimental effects of microsegregation in these cast steel components. The presence of very fine microstructures results in ultra-high strength with low ductility cast steel.

Preparation and Characterization of Ni-Mn-Ga-Cu Shape Memory Alloy with Micron-Scale Pores

Porous Ni-Mn-Ga shape memory alloys (SMAs) were prepared by powder metallurgy using NaCl as a pore-forming agent with an average pore size of 20–30 μm. The microstructure, phase transformation, superelasticity, and elastocaloric properties of the porous alloys were investigated. The prepared porous alloy had a uniform pore distribution and interconnected microchannels were formed. Cu doping can effectively improve the toughness of a porous alloy, thus improving the superelasticity. It was found that porous Ni-Mn-Ga-Cu SMAs have a flat stress plateau, which exhibits a maximum elongation of 5% with partially recoverable strain and a critical stress for martensite transformation as low as about 160 MPa. In addition, an adiabatic temperature change of 0.6 K was obtained for the prepared porous alloy at a strain of 1.2% at about 150 MPa. This work confirms that the introduction of porous structures into polycrystalline Ni-Mn-Ga SMAs is an effective way to reduce costs and improve performance, and provides opportunities for engineering applications.

Enhancing mechanical properties in Ti-Containing FeMn40Co10Cr10C0.5 High-Entropy alloy through Chi (χ) phase dissolution and precipitation hardening

This research investigates the effects of adding 2 at.% Ti on the microstructure, phase transformation, and mechanical properties of FeMn40Co10Cr10C0.5 high-entropy alloy (HEA) in both as-cast and homogenized conditions. The incorporation of Ti increased the lattice parameter of the FCC matrix and caused greater lattice distortion (∼5.9 %) due to the larger atomic radius of Ti. The negative mixing enthalpy of Ti resulted in segregation at interdendritic regions, forming a Ti-rich Chi (χ) phase during solidification. The as-cast structure displayed a dendritic microstructure consisting of 77.9 % FCC, 20.6 % χ, and 1.5 % TiC phases. After homogenization at 1200 °C for 2 h, the χ phase was dissolved, increasing the volume fraction of TiC to 24 %. The homogenized sample exhibited a substantial improvement in tensile properties, i.e., with the ultimate tensile strength (UTS) rising from 631 MPa in the as-cast condition to 689 MPa, and yield strength (YS) increasing from 346 MPa to 419 MPa, while maintaining an elongation of ∼ 54 %. These enhancements are attributed to solid solution strengthening, increased carbide precipitation, and the dissolution of the χ phase into the FCC matrix.